Liquid crystal display elements have been used in various devices such as measuring equipment, automotive panel word processor, electronic note, printer, computer, TV, clock, advertisement panel board, and etc., including watch and electronic calculator. The representative of the liquid crystal display method includes TN (twisted nematic) type, STN (super twisted nematic) type, vertical alignment type using a TFT (thin film transistor), and IPS (in-plane switching) type. Liquid crystal compositions used for such liquid crystal display devices need to satisfy the requirements as follows: they are stable to external elements such as moisture, air, heat, and light: having a liquid crystal phase (nematic phase, smectic phase, and blue phase, and etc.) in a broad temperature range as possible including room temperature as a center thereof; having a low viscosity; and enabling a low driving voltage. Furthermore, the liquid crystal composition comprises several to several tens of compounds in order to optimize the value of the dielectric constant anisotropy (Δ∈) and a refractive index anisotropy (Δn) depending on individual display element.
In all driving types such as such as TN type, STN type, and IPS type, there have been demands to improve the response speed, and in order to satisfy such demands, a liquid crystal composition having a lower viscosity than present liquid crystal compositions is required. In order to develop a liquid crystal composition having a low viscosity, it is known to be extremely effective to employ a non-polar compound, that is, a compound which show almost no Δ∈. For such a non-polar compound, it is demanded to have a suitable transparent point (T-i), Δn, and a low viscosity. Also, a high stability to heat, light and etc., is required when it is uses as a liquid crystal composition for display element.
Conventionally, compounds having a cyclohexylvinyl structure or an allyl ether structure are used as a non-polar compound. A compound having an allyl ether structure is a useful compound that indicates a relatively low viscosity. For example, the compound shown below is disclosed as a compound having an allyl ether structure (Patent Reference No. 1). However, this compound is not large enough in its Δn and has a problem of relatively low miscibility with other liquid crystalline compounds.
(In the formula, R represents a linear alkyl group with a carbon atom number of 1 to 9.)
On the other hand, for example, as a compound having a structure in which hydrogen atom of a benzene ring was substituted with fluorine atom, the compound shown below is disclosed (Patent Reference No. 2, Patent Reference No. 3).

(In the formula, Y and Z each independently represent an alkyl group and an alkoxy group having a carbon atom number of 1 to 12.)

(In the formula, R1 and R2 each independently represent an alkyl group and an alkoxy group having a carbon atom number of 1 to 12.)
Furthermore, a compound having an allyl ether structure and a substituent of a halogen atom, as shown below, is disclosed (Patent Reference No. 4). However, the values of Δn thereof are not large enough.
